Trance possession is an important part of our religion. During a bembé or drumming party for the orishas an orisha may be persuaded to join the party by entering the body of one of the priests consecrated to that orisha. This is referred to as the person being 'mounted' by the orisha or that the orisha has 'come down' from heaven to be with us. The songs, rythms and dances are actually calculated to entreating the orishas to come down so that we may be blessed by their counsel, cleansings and their sheer presence. When an orisha decides to use one our bodies for a time it is, of course, a cause of great joy for us.
The orishas only rarely mount an aleyo or person who has not been initiated as a priest, and then usually only to point this person out as a person who needs to be initiated as a priest or priestess in the religion. It is not forced on people nor is it a thing of evil such as portrayed in movies like "The Exorcist" nor does anyone spit pea soup. If someone is not ready, the orisha will be gently persuaded to leave until the person is initiated and prepared for such an event. And anyone who has experienced being 'touched' or actually mounted will tell you the profound feelings of joy and wisdom that accompany the presence of these great spiritual beings known as orishas.